Recirculating aquaculture systems (RAS) generate waste streams rich in nitrogen and phosphorus, creating both environmental challenges and operational costs. A recent BARD‑supported U.S.–Israel research project led by the University of Massachusetts Dartmouth, in collaboration with Israel’s National Centre for Mariculture at the Israel Oceanographic and Limnological Research (IOLR) institute, demonstrates how these waste streams can be transformed into valuable fertilizer products through targeted nutrient recovery.
The research project led by Prof. Sukalyan Sengupta in partnership with Dr. Tal Shay and Dr. Uri Yogev focused on modifying chabazite, a naturally occurring zeolite, using alkaline hydrothermal treatment to enhance its capacity and selectivity for ammonium (NH₄⁺). Extensive material characterization confirmed that the treatment fundamentally alters the zeolite structure, converting chabazite into an aluminum‑dense analcime framework with a much lower silica–alumina ratio. This transformation nearly doubled the ammonium removal capacity of the material, reaching 4.19 meq/g (75.6 mg NH₄⁺/g).
In fixed‑bed experiments simulating aquaculture wastewater, the modified zeolite selectively removed ammonium in the presence of competing ions such as sodium, calcium, and magnesium. Importantly, regeneration using brine recovered approximately 94% of the captured ammonium in a concentrated solution that can be reused directly as a nitrogen fertilizer or combined with phosphorus for struvite production. Multiple adsorption–regeneration cycles showed stable performance and reusability.
Together with complementary phosphorus recovery technologies and system‑level integration in operational RAS units, this work illustrates a practical pathway for turning aquaculture wastewater from a disposal burden into a source of recoverable nutrients, thus supporting circular economy approaches in intensive aquaculture.
Read more about this research: Modified zeolite in a sustainable, circular economy-based process for enhanced ammonium recovery from wastewater – ScienceDirect
